Among the changes Google didn't mention that are nestled in Android 12 Developer Preview Two is a new widget picker for the Pixel Launcher. This new picker still organizes things on a side-scrolling per-app basis, but collapsed for easier perusal.

 

Left: Android 12 DP1. Right: Android 12 DP2.

Previously, Google organized widgets into expanded side-scrolling categories, grouped alphabetically by app and then by widget name. In DP2, these app categories are by default collapsed, and tapping them expands the list of the app's associated widget. This means you can scroll through your list of widgets that much faster.

Dark theme and the collapsed view. 

This relatively subtle tweak may not be in-your-face or always visible, but it should make selecting the appropriate widget just a tiny bit faster even with the added tap to expand an app category, and objectively it's a cleaner and less busy look.